Method of making a biomedical electrode

ABSTRACT

A biomedical electrode which generally comprises a conductor member partially overlapping a separator construction. The conductor member is preferably a thin flat, flexible member having a pad portion and a tab portion. The tab portion overlaps the separator construction in a manner which centrally positions mechanical and electrical contact of electrode with an electrical lead to electrical instrumentation. Beneath pad portion and all or a substantial portion of separator construction is a conductive adhesive to provide good electrical interface between skin of a subject and the electrical instrumentation. Methods of manufacturing biomedical electrodes from strips of components are also disclosed.

This is a division of application Ser. No. 07/686,138 filed Apr. 16,1991, now U.S. Pat. No. 5,133,356 issued Jul. 8, 1992.

FIELD OF THE INVENTION

The present invention relates to flexible, low-profile, skin-adherinqbiomedical electrodes which have an electrically conductive contactingtab centrally-positioned on an outer surface and within a perimeter ofthe biomedical electrode.

BACKGROUND OF THE INVENTION

Electrocardiography is the well-established, but still rapidlydeveloping, science of making and studying graphic records(electrocardiograms) generated by electrical currents originating in ananimal heart, most often a mammalian heart.

An electrocardiogram (ECG) is measured through utilization of anelectrocardiograph instrument, which monitors the electric potentialsassociated with those electric currents that transverse the heart.

In practice, electrodes are positioned on the skin surface of thesubject to be evaluated. Those electrodes are in electricalcommunication with the electrocardiograph instrumentation. Theelectrodes must generally be such as can accurately detect and transmitelectrical signals produced by various biological events.

An acceptable biomedical electrode has an adequate conductive surfacefor receipt of electrical signals from the body, a good conductiveinterface between the electrical instrumentation and the subject, andsufficient adherence of the electrode during the period of evaluation.

Electrocardiography has been applied in a variety of circumstancesincluding: in resting diagnostic procedures; in surgical and emergencyroom procedures; in cardiac units; in critical care units; in ambulatorymonitoring; in stress diagnostic procedures; and in more continual, orintermittent, monitoring as selected for a person not under constantsupervision and not substantially restrained with respect to activity.

Thus, the period of evaluation and the condition of evaluationenvironment can differ among the various types of ECG procedures

Regardless of the period of evaluation or condition of evaluationenvironment, an acceptable biomedical electrode must perform adequatelyto be a useful evaluation component: adequate conductive surface, goodconductive interface, and continued skin adherence during the period ofevaluation.

Another factor in the acceptability of a biomedical electrode is cost.Due to hygiene and other expense of re-use considerations, manybiomedical electrodes are designed to be disposable after a single use.Biomedical electrodes used during limited periods of evaluation, such asresting, emergency, or surgical diagnosis, can be constructed and pricedfor a single use before disposal.

Biomedical electrodes have been known to provide an electricallyconductive tab extending beyond the perimeter of the conductive surfacearea of the biomedical electrode. Examples of biomedical electrodes ofthis type are disclosed in U.S. Pat. No. 4,539,996 (Engel), U.S. Pat.No. 4,543,958 (Cartmell), U.S. Pat. No. 4,694,835 (Strand), and U.S.Pat. No. 4,852,571 (Gadsby et al.). An electrically conductive tabextending beyond the perimeter of the conductive surface area of thebiomedical electrode requires mechanical and electrical contact in anarea adjacent to skin of a subject.

Other biomedical electrodes provide an electrically conductive tabwithin the perimeter of the conductive surface area of the biomedicalelectrode by having the tab emerge from a skin contacting side of theelectrode through a slit or seam in the outer protective layer of theelectrode. Examples of biomedical electrodes of this type are disclosedin U.S. Pat. No. 1,622,446 (Wappler), U.S. Pat. No. 4,166,465 (Esty),U.S. Pat. No. 4,852,571 (Gadsby et al.), European Patent Publication 0360 496 (Strand et al.), and British Patent Specification 1 519 782(Osborn et al.). Production of electrodes of this type require elaboratemanufacturing techniques to make a slit or form a seam, with the tabextending therethrough.

Still other biomedical electrodes provide an electrically conductive tabwithin the perimeter of the conductive surface area of the biomedicalelectrode by having the outermost protective layer cut along a linewithin the perimeter of protective layer to form a tab from theprotective layer. Examples of biomedical electrodes of this type aredisclosed in U.S. Pat. No. 4,657,023 (Kuhn), U.S. Pat. No. 4,679,563(Wada et al.), and U.S Pat. No. 4,922,911 (Wada et al.). Production ofelectrodes of this type also require elaborate manufacturing techniquesto make a cut in the outermost protective layer and creating anelectrically conductive tab therefrom which can be lifted from theremainder of the protective layer for use.

SUMMARY OF THE INVENTION

The present invention provides an inexpensively-made biomedicalelectrode which has a good conductive surface area, good conductiveinterface between the subject of evaluation and the electricalinstrumentation, and sufficient adherence of the electrode to the skinof the subject for the period of evaluation and the conditions of theevaluation environment.

The biomedical electrode of the present invention comprises (a) aseparator construction comprising a flat sheet having a first and secondopposite sides and edges between the sides defining a perimeter; and (b)a conductor member having a pad portion and a tab portion, the conductormember being oriented in the electrode with the pad portion having aside coplanar with the second side of the separator construction, andwith the tab portion in a plane above and overlapping the first side ofthe separator construction; the tab portion having an area smaller thanan area of the first side of the separator construction wherebymechanical and electrical connection of the biomedical electrode iscentrally-positioned within the perimeter.

In this description, "centrally-positioned" means that the conductormember is secured or otherwise aligned to the separator construction ata position on the first side of the separator construction such that thetab portion of the conductor member does not extend beyond a perimeterof the biomedical electrode.

The biomedical electrode of the present invention further comprises afield of conductive adhesive contacting the side of the pad portion andoptionally also the second side of the separator construction. Thebiomedical electrode further comprises means of adhering the conductormember to the first side of the separator construction, whereby theconductor member tab portion is adjacent to, but not adhered directlyto, the separator construction.

Biomedical electrodes according to the present invention include asubstantially flat, flexible, conductor member having a pad portion anda tab portion. The pad portion is arranged and oriented to receiveelectrical signals from the subject's body. The tab portion, on theother hand, is available for engagement with a wire lead or the like, toprovide electrical communication to electrical instrumentation such asan electrocardiograph monitor.

Substantially flat conductor members according to the present inventioncan be formed from a relatively thin layer of flexible polymericmaterial, such as a polyester film, having a conductive layer, such as asilver/silver chloride material, a metal foil or laminate, (e.g., avinyl-laminated tin foil), or a non-woven web impregnated withconductive carbon ink, on at least one side thereof. Preferred suchmaterials, being relatively thin, are very flexible, and can be readilyand easily mounted in the arrangements required by the invention.Further, depending on the nature and amount of metal employed, they canbe relatively transparent to X-ray, so a person wearing biomedicalelectrodes according to preferred embodiments of the present inventioncan be examined by X-ray without significant problems from strongshadows. That is, the person need not be bothered by removal andremounting of the biomedical electrodes, in order for routine X-rayexaminations or the like to occur.

Conductive adhesive capable of biocompatibly adhering to skin can begenerally either a conductive adhering or "sticky" gel or a conductivepressure-sensitive adhesive. A variety of conductive adhesives known tothose skilled in the art can be utilized to provide both good electricalinterface between the subject and the electrical instrumentation andgood adhesion during the period of evaluation of the subject.Non-limiting examples of conductive adhesives include conductiveadhesives disclosed in U.S. Pat. Nos. 4,539,996; 4,554,924; and4,848,353 (all Engel and incorporated by reference herein) and U.S. Re.Pat. Nos. 31,454 (Hymes) and 4,391,278 (Cahalan).

A separator construction segregates the conductive material from the tabportion of the conductor member and also protects the conductiveadhesive from contact with the environment during the period ofevaluation. The separator construction can be made of a number ofelectrically insulative materials, preferably polymeric film materials,and more preferably, transparent or translucently polymeric filmmaterials. Transparency or translucency through the separatorconstruction permits visual inspection of the condition of theconductive adhesive and its interface with and condition of skinbeneath. Non-limiting examples of polymeric film materials includepolyolefins (e.g., polyethylene and polypropylene), polyesters, andpolyurethanes.

Alternatively, the separator construction can have an electricallyconductive surface on the side contacting conductive adhesive. Theelectrically conductive surface can be useful to increase surface areaof electrical interface between conductive adhesive and the pad portionof the conductor member. Certain diagnostic and monitoring circumstancescan require such larger surface area. Alternatively, the biomedicalelectrode of the present invention can distribute electrical energy toskin of a subject, as in electrotherapy. In that instance, having anelectrically conductive surface area on separator construction canevenly distribute such electrical energy to all areas of the conductiveadhesive.

Optionally, a means to adhere the conductor member to the separatorconstruction can be employed to centrally-position the conductor memberon the biomedical electrode. Non-limiting examples of the means ofadhering can include a separate field of pressure-sensitive or hot meltadhesive, a double-stick pressure-sensitive adhesive tape, or a portionof the separator construction having an adhesive surface contacting theconductive adhesive being folded back to provide an adhesive surface tocontact the conductor member.

The field of conductive adhesive can contact substantially the entirearea of both pad portion of conductor member and the entire area ofseparator construction accessible for contact. Alternatively, the fieldof conductive adhesive can contact substantially the entire area of padportion of conductor member and a biocompatible skin adhesive cancontact substantially the entire area of separator construction.

Preferably, a portion of separator construction can extend beyond thefield of conductive adhesive or skin adhesive contacting the remainderof separator construction, to create a non-adhering lift tab tofacilitate placement and removal of the electrode prior to and at theconclusion of the period of evaluation.

In general, when first manufactured the biomedical electrode willinclude a protective release liner or the like secured to the first sideof the insulator construction. The release liner can be selectivelyseparated from the conductive adhesive to expose its outer surface forapplication to a subject. A variety of materials may be utilized as arelease liner, for example a silicone-coated polypropylene or polyestermaterial might be utilized.

The release liner can be coterminous with the dimensions of the adhesiveareas of the biomedical electrode or can extend beyond the dimensionsthereof.

In other embodiments, a spacer or tab positioned between a portion ofthe release liner and the conductive adhesive can be used to facilitateseparation.

Also, an array of biomedical electrodes can be arranged on a singlerelease liner, with the number of electrodes on the liner being chosenfor convenience of the health care practitioner.

It is a feature of the present invention that the centrally-positionedtab portion facilitates ease of good, secure, conductive connection toan electrocardiograph lead.

It is another feature of the present invention that the biomedicalelectrode is constructed of flexible, conformable materials to maximizeadherence of the biomedical electrode to skin of a subject regardless ofthe contours of skin where adhesion must occur.

It is another feature of the present invention that the biomedicalelectrode is constructed of relatively thin materials to provide alow-profile which minimizes obstruction or disruption with otherequipment, clothing, manual medical procedures or the like.

It is another feature of the present invention that the biomedicalelectrode is constructed of materials less likely to cause an image onX-ray photographs of the area of the subject near the location ofelectrode placement.

It is another feature of the present invention that thecentrally-positioned tab portion provides good, secure, conductiveconnection to an electrocardiograph lead within the perimeter of thebiomedical electrode.

It is another feature of the present invention that thecentrally-positioned tab portion facilitates connection to electricalinstrumentation without application of significant deleterious stress tothe adhesive interface between the electrode and the subject. Ingeneral, this avoidance of stress to the biomedical electrode minimizesadhesive failure at the skin surface.

It is another feature of the present invention that the biomedicalelectrode provides a good conductive interface between the electrode andthe subject's body. In general, this is provided by use of a conductiveadhesive positioned between a conductive portion of the electrode andthe subject's body.

It is another feature of the present invention that the biomedicalelectrode is configured and made of materials to maximize flexibilityduring use. For example, due to its flexible construction, thebiomedical electrode of the present invention can be easily positionedin engagement with a portion of a subject's body. Should the subjectmove or twist while the biomedical electrode of the present invention isin position, the electrode can readily flex or bend to accommodate themovement and/or twists of the subject's body.

It is an advantage of the present invention that ends of the leadsattachable to the electrodes possibly having electrically conductiveportions at least partially exposed thereat are unlikely to come intodirect contact with a subject's body; come into direct contact withelectrolyte gel and/or conductive adhesive; and/or come into contactwith adjacent leads and/or electrodes. As a result, better electricalsignals can be recorded without interfering signals. Also as a result,leads or other clips are less likely to become contaminated or dirtywith body exudate, conductive adhesive and the like.

It is another advantage of the present invention that biomedicalelectrodes can be made relatively inexpensively and efficientlyconstructed.

Methods of construction of the biomedical electrode can provide a massproduction of an array of electrodes on a single release liner withoutthe need for establishing the position of the tab portion through a slitor seam or formed from a portion of the outermost layer of theelectrode.

Sequential layering of components of biomedical electrodes canfacilitate mass production of an array of electrodes, which are thenseparated by cutting into individual electrodes while on the releaseliner.

A method of making biomedical electrodes comprises (a) positioning on arelease liner a strip of conductive adhesive having opposing first andsecond edges along the strip; (b) overlaying a strip of separatorconstruction, having opposing first and second edges along the separatorconstruction strip, on the conductive adhesive in a position of thefirst edge of the separator construction relative to the first edge ofthe conductive adhesive strip; (c) overlaying a means for adhering onthe separator construction in a position relative to the second edge ofthe separator construction; (d) overlaying a strip of conductor members,each having a tab portion, a pad portion, and pad portion edge, on theconductive adhesive and the means for adhering in a position of each padportion edge aligned with the second edge of the conductive adhesive toform an electrode subassembly, whereby the tab portion is in a planeabove and overlapping the strip of separator construction; and (e)separating the electrode subassembly between adjacent tab portions ofthe conductor members.

Another method of making biomedical electrodes of the present inventioncomprises (a) providing a strip of conductor members, each member havingtwo tab portions at opposing edges of the strip and two pad portionsintegral and continuous on the strip; (b) overlaying a means foradhering on the strip of conductor members on each tab portion in aposition substantially adjacent to each pad portion; (c) overlaying aseparator construction on each means for adhering and over each tabportion of each conductor member; (d) overlaying a field of conductiveadhesive over each pad portion of each conductor member and optionallyover each separator construction to form an electrode array; (e)overlaying a release liner on the electrode array; (f) cutting theelectrode array on the release liner along a line between adjacent tabportions; and (g) cutting the electrode array along a line betweencontinuous pad portions, whereby a plurality of individual biomedicalelectrodes, each having a centrally positioned tab portion, are providedon the release liner.

It is another feature of the present invention that relativelyinexpensive components and mass manufacturing techniques can beutilized.

It is an advantage of the present invention that an inexpensively-made,flexible, low-profile, biomedical electrode can provide a goodconductive surface area, good conductive interface, and adherence toskin for the period of evaluation.

The use of the biomedical electrode of the present invention candemonstrate its advantages over other biomedical electrodes previouslyknown and used.

A lead from electrocardiograph or other electrical instrumentation isattached to the tab portion.

Biomedical electrodes of the present invention can be used with a numberof types of biomedical instrumentation. Biomedical electrodes of thepresent invention can be used with electrocardiographs or otherelectrical receiving instrumentation for diagnostic, monitoring, stress,or other testing detecting a subject's electrical signals. Biomedicalelectrodes of the present invention also can be used with therapeuticelectrical instrumentation such as transcutaneous electronic nervestimulation (TENS) devices used for pain management and neuromuscularstimulation (NMS) used for treating conditions such as scoliosis.Biomedical electrodes of the present invention also can be used asdispersive electrodes or "grounding plates" for electrosurgery or asdefibrillation pads for cardiac emergency treatment. Typically, theelectrical connection is provided by means of a clip or clasp elementwhich can be attached to the conductor member tab portion. Due to thelocation of the tab portion positioned centrally on the outer surface ofthe electrode, the clip or clasp, having electrically conductiveelements therein, is insulated from direct contact with the subject'sbody. That is, it is unlikely that the clip or clasp will receiveelectrical signals other than through the conductive member. As aresult, the arrangement of the present invention provides for relativelylow likelihood of unintended noise interrupting the desired signal to bereceived by the electrical instrumentation. Further, it is most unlikelythat a clip will contact or pinch skin of a subject of evaluation orthat a reusable clip will become contaminated by body oils or adhesive.Further, it is unlikely that twisting of clip or clasp duringinadvertent movement of the subject relative to the electricalinstrumentation will cause a loss of adhesion of the electrode at theskin of the subject.

It will be seen from the embodiments of the invention and drawingsdescribed below that an insulation of the clip or clasp from thesubject's body is achieved in a secure manner without the need foradhesive tape or the like being used to maintain or retain the clip inposition. This facilitates attachment and detachment of the clip asnecessary, and further facilitates subject comfort.

The drawings constitute a part of this specification and representpreferred embodiments of the invention. It will be understood that, insome instances, relative component sizes and/or material thicknesses maybe shown exaggerated, to facilitate an understanding of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a biomedical electrode according to thepresent invention, shown in an environment of association with anelectrocardiograph monitor and with a lead extending from the electrodeto the monitor.

FIG. 2 is a top plan view of a biomedical electrode according to theembodiment of FIG. 1; dotted lines indicating selected portions hiddenfrom view.

FIG. 3 is an enlarged side cross sectional view taken generally alongline 3--3, of FIG. 2, except that the device of FIG. 3 does include arelease liner.

FIG. 4 is a top plan view of a second embodiment of a biomedicalelectrode; dotted lines indicating selected portions hidden from view.

FIG. 5 is an enlarged side cross sectional view taken generally alongline 5--5, of FIG. 4, except that the electrode of FIG. 5 does include arelease liner.

FIG. 6 is a top plan view of a one embodiment of an assembly ofbiomedical electrodes.

FIG. 7 is an illustrative view of first steps of a means of assembly ofa biomedical electrode subassembly useful for providing a strip ofbiomedical electrodes.

FIG. 8 is a top plan view of a second embodiment of an assembly ofbiomedical electrodes.

FIG. 9 is an illustrative view of first steps of a means of assembly ofa biomedical electrode array useful for providing the assembly ofbiomedical electrodes shown in FIG. 8.

Embodiments of the Invention

Detailed descriptions of certain embodiments of the present inventionare provided hereinbelow. It is to be understood that the embodimentsdescribed and shown are representative only, and that the presentinvention may be embodied in various forms not depicted or specificallydescribed in detail.

The reference numeral 1, in FIG. 1, generally designates a biomedicalelectrode according to the present invention. The electrode 1 isdepicted in perspective, and is shown in association with electricaldiagnostic instrumentation 2, such as an electrocardiograph monitor.Monitor 2 can be portable, mobile, or stationary.

Electrical communication between electrode 1 and instrumentation 2 isgenerally provided by means of a lead 5 having a first end 6 attached toa clip or clasp 7, and a second end 8 attached to a jack 9 or the like,for engagement with instrumentation 2. A variety of clips 7 may beutilized. The one shown in FIG. 1, includes a thumb operated cam 10which, when slid in the direction indicated by arrow 11, causes grippingof a thin, flat member, in particular a tab portion of electrode 1described below. Clip 7 is described in U.S. Pat. No. 4,700,997(Strand), which is incorporated by reference herein. Other clips usefulincluding "alligator" clips commonly used in the art and a clipdescribed in U.S. Pat. No. 4,842,558 (Strand) which is incorporated byreference herein. Alternatively, the mechanical and electrical contactat tab portion can be pre-wired to a lead wire 5, which is useful incertain circumstances where attachment of a clip to an electrode isdifficult, such as with premature infants.

Electrodes 1 according to the present invention include two primarynon-adhesive components: a flexible separator construction 15 and asubstantially flat, flexible, conductor member 16. A preferredassociation between conductor member 16 and separator construction 15yields many of the advantages of the present invention.

Still referring to FIG. 1, conductor member 16 generally includes a tabportion 18 and a pad portion 19. According to the present invention, theconductor member 16 is oriented relative to the separator construction15 such that the pad portion 19 is substantially coplanar with theseparator construction 15 and the tab portion 18 is generally above theplane of the insulator construction 15 and the pad portion 19.

It is noted that tab portion 18 of conductor member 16 includes thatportion of the conductor member 16 engagable by clip 7. Typically, forpreferred embodiments, the tab portion 18 will be a rather elongate,narrow, extension of conductor member 16. Other shapes are contemplatedas also useful, provided that the tab portion remainscentrally-positioned. A non-limiting example includes a shape of tabportion 18 that has a larger surface area for mechanical and electricalcontact but which remains within the perimeter of the biomedicalelectrode 1.

The pad portion 19 of conductor member 16 is that portion of theconductor member 16 which receives electrical signals from the subject'sbody. In general, it is preferred that the pad portion 19 be relativelylarge in gross surface area. The term "gross surface area" used hereinmeans the surface area resulting from the overall outside perimeterdimensions of pad portion 19, and not necessarily to that surface areawhich can be measured by microscopic examination of the conductorsurface of pad portion 19. The term "surface area" or "gross surfacearea" as used herein in this context is meant to refer to one side onlyof the pad portion 19. For typical, preferred embodiments of the presentinvention, to be used as adult human bioelectrodes, the pad portion 19should have an overall surface area of about 0.65 to 6.5 cm². Also, thetab portion 18 should have an overall length of about 1.0-3.0 cm and awidth of about 0.6-2 cm. It is noted that the pad portions shown in thedrawings are roughly 60% wider than they are long, however a variety ofsizes and shapes may be used.

FIG. 1 also shows that a field 20 of conductive adhesive is applied toconductor member pad portion 19 and optionally to separator construction15 on the surfaces opposite from exposure to clip 7. The conductiveadhesive 20 is generally either an adhering or "sticky" electrolyte gel,or a conductive pressure-sensitive adhesive. For preferred embodimentsof the present invention, conductive pressure-sensitive adhesive isused, as it provides not only for good conductive association betweenthe pad portion 19 and the user's body, but it also facilitatesadhesion, i.e., maintenance over time of a good association. A varietyof conductive adhesives may be utilized, and all that is generallyrequired is that the material function to provide for good electricalcontact between pad portion 19 and the subject's body. Preferredconductive adhesives are described in greater detail below.

The size and configuration of tab portion 18 shown in FIG. 1 illustratesthe advantages of a biomedical electrode 1 of the present invention. Thetab portion 18 entirely resides within the perimeter of electrode 1,comprising the edges of conductor member pad portion 19 and separatorconstruction 15. The tab portion also resides in the plane aboveseparator construction but is sized and shaped to reside within itsperimeter.

Thus, the tab portion 18, and any clip 7 in association therewith, iscompletely insulated or separated from the user's body by the separatorconstruction 15. In this manner, direct contact between clip 7 (and anyconductive elements thereon), and the user's body is unlikely. This willinhibit the generation of undesired noise or signals in the system forelectrocardiograph monitoring. Further, direct contact between a clip 7and the user's body is minimized for other electrical instrumentation.

The substantially flat construction depicted in FIG. 1 leads tosignificant advantages. For example, it is foreseen that as the userattaches or detaches clip 7, or goes about ordinary movement withelectrode 1 and clip 7 in position, significant tugging or pulling ontab portion 18 may occur. For the most part, due to the flatconstruction of electrode 1, the major component of this force willtypically be directed in the general direction indicated by arrow 30.That is, it will generally be directed parallel to a plane of flatelectrode 1 and parallel to the body of a user to which electrode 1 maybe attached. This type of force is a shearing force operating on thefield 20 of conductive adhesive between separator construction 15 andthe user's body. Since there is relatively little component causing muchseparation between the two, but rather most of the tugging componentwill be shear, separation will be less likely to occur. This can be asignificant advantage to the present invention, over arrangementswherein a less flat construction is utilized. Alternately phrased, theconstruction of the electrode 1 is such that typical forces due totugging on the lead wire 5 are not likely to "lift" the electrode 1 fromthe subject.

The centrally-positioned tab portion 18 also resists the effects oftwisting of the mechanical contact between the lead wire 5 andelectrode 1. By securement of the conductor member 16 to the separatorconstruction 15 in a location that centrally positions the tab portion18, typical forces due to twisting on the lead wire 5 are less likely totwist and lift any edge of the electrode.

Another advantage of the rather flat construction is that the electrode1 will be less conspicuous when worn under the user's clothes and lessobstructive to other medical procedures. Further, the arrangement can bereadily manufactured, manipulated and applied.

It will also be understood that the rather flat, flexible constructiondoes not provide for any substantial projections that might be likely tocause discomfort for a user, should the user be bumped in the vicinityof the worn electrode or should the subject lie down.

A further view of an embodiment of the invention is depicted in FIGS. 2and 3. Referring to FIG. 2, the electrode 40 depicted therein isgenerally the same as electrode 1 in FIG. 1. Electrode 40 includes aninsulating separator construction 41, a conductor member 42, a field 43of adhesive contacting areas of both separator construction 41 andconductor member 42, and an adhesive means 44 between separatorconstruction 41 and conductor member 42.

As seen in FIG. 3, field 43 of adhesive can be separated into twoportions: portion 43a which contacts conductor member 42 and portion 43bwhich contacts separator construction 41. Whereas field portion 43a is aconductive adhesive, field portion 43b can be a biocompatible adhesive,such as a conductive adhesive or a biocompatible skin adhesive which isnot necessarily conductive. Depending on the surface area of electricalinterface desired, the relative sizes of field portions 43a and 43b canalso vary, so long as an adequate area of field portion 43a contactsconductor member 42 to provide useful electrical interface.

For the embodiment of FIG. 2, the separator construction 41 has oppositesides 45 and 46, with side 45 being an exposed surface near connectionof conductor member 42 with clip 7 and surface 46 being in contact withfield 43 of conductive adhesive in both portions 43a and 43b. Betweenopposite sides 45 and 46 are opposing edges 47 and 48, with edge 47proximal to conductor member 42 and edge 48 distal to conductor member42. Separator construction 41 has opposing edges 49 and 50 between edges47 and 48 to define an area "A" on side 45. Separator construction side45 has a larger surface area "A" than the surface area "B" of anyportion of conductor member 42 in a plane above side 45. Thecombinations of edges 47, 48, 49, and 50 define a perimeter of thesurface area "A" within which conductor surface area "B" is contained.

Conductor member 42 has a pad portion 51 generally corresponding to padportion 19 in FIG. 1 and a tab portion 52 generally corresponding to tabportion 18 in FIG. 1. Pad portion 51 has an exposed side 53 and aconductive interface side 54 opposed thereto (as seen in FIG. 3).Between sides 53 and 54 are an edge 55 distal to the separatorconstruction 41 and a curving edge 56 which defines the shape of tabportion 52 in the plane above area A of the separator construction 41.Shape of tab portion 52 is defined by the shape of curving edge 56,which can vary in any manner which result in an area "B" within area"A". Between edges 55 and 56 are opposing edges 57 and 58 which define awidth of pad portion 51 approximately the same width as the width ofseparator portion 41 between edges 49 and 50.

Tab portion 52 defined by curving edge 56 overlaps side 45 of separatorconstruction 41. As seen in FIG. 3, tab portion 52 is above a planedefined by the relative coplanar positions of separator construction 41and pad portion 51. As seen in FIG. 2, area B comprising the portion ofoverlap of tab portion 52 over separator construction 41 iscentrally-positioned within the edges 48, 49, and 50 of side 45 ofseparator construction 41.

To secure the relative position of tab portion 52 above the side 45 ofseparator construction 41, a means for adhering, e.g., a strip 44 ofadhesive is placed at the point of overlap of tab portion 52 over edge47 of separator construction 41. As seen in FIG. 2, this strip 44extends substantially between edges 57 and 58 of conductor member 42 andsubstantially adjacent to the points of intersection of curved edge 56with edges 57 and 58.

Strip 44 also raises slightly tab portion 52 from contact with side 45of separator construction 41, such that tab portion 52 is adjacent to,but not directly adhered to, separator construction 41 at side 45. Thisslight elevation of tab portion 52 above side 45 also facilitates themechanical and electrical connecting of tab portion 52 with clip 7 asseen in FIG. 1.

Contacting side 54 of pad portion 51 of conductor member 42 is a fieldportion 43a of conductive adhesive. In this embodiment, conductiveadhesive is also used as field portion 43b to contact side 46 ofseparator construction 41, although conductive adhesive can be replacedby a skin adhesive. As seen in FIG. 2, field 43 substantially extendsfrom edge 57 to edge 58 beneath pad portion 51 and from edge 49 to edge50 beneath separator construction 41. Also, field 43 substantiallyextends from edge 48 of separator construction 41 to edge 55 of padportion 51. Side 54 of pad portion 51 provides good electrical andadhering contact between pad portion 51 and field portion 43a. Side 46of separator construction 41 provides protection of field portion 43bfrom exposure to the environment.

Thus, the positioning and securement of conductor member 42 on side 54causes the establishment of a good electrical interface between fieldportion 43a and conductor member 42, and the establishment of a fieldportion 43a, and optionally field portion 43b, of conductive adhesive ofadequate size and sufficient adhering properties to maintain goodelectrical interface between the electrical instrumentation and the skinof the subject for the period of evaluation.

In FIG. 3, a layer of release liner 60 is shown positioned against thatside of electrode 40 which has field 43 of adhesive(s) thereon.Preferably, the release liner 60 will directly contact only field 43 andnot other components of electrode 40.

In general, after manufacture and during storage, electrode 40 will bemaintained with release liner 60 protecting the field 43 of adhesive(s).It is foreseen that the release liner 60 will generally be stripped fromthe arrangement 40 immediately prior to use. A variety of release liners60 may be utilized; for example, a liner comprising a polymer such as apolypropylene or polyester material, coated with a silicone release typecoating which is readily separable from the skin adhesive and conductiveadhesive. In some embodiments, it may be desired to place a spacer ortab (not shown) between release liner 60 and a portion of field 43 ofadhesive(s) to facilitate the separation.

It will be understood that the dimensions of the various layers, andtheir conformation during association, are shown somewhat exaggerated inFIG. 3, to facilitate an understanding of the invention. In general, anoverall substantially flat appearance with only a very minor "s" typebend between pad portion 51 and tab portion 52 of conductor member 42 isaccommodated by the arrangement.

FIGS. 4 and 5 illustrate an alternate embodiment of the biomedicalelectrode of the present invention.

Biomedical electrode 70 conforms in analogous respect to biomedicalelectrode 40 seen in FIGS. 2 and 3 with some exceptions. Separatorconstruction 71 differs from separator construction 41. At a locationdistal from conductor member 72, separator construction 71 extendsbeyond field 73 of adhesive at portion 73b distal from field portion73a. There, separator construction 71 provides a lift tab portion 74 forfacile removal of electrode 70 from a release liner 76, placement ofelectrode on skin of a subject, and subsequent removal of electrode 70from skin of a subject at the end of the evaluation period. The edge ofthe lift tab portion 74 can be curved as seen in FIG. 4 to minimize acorner snagging on clothing or equipment during use.

Referring to FIG. 5, the remaining portions of electrode 70 areanalogous to electrode 40. Conductor member 72 has a pad portion 77contacting field portion 73a of conductive adhesive and a tab portion78. Conductor member 72 is adhered to separator construction 71 by adouble stick adhesive strip 79 positioned at the area of overlap of tabportion 78 over separator construction 71.

Biomedical electrode 70 seen in FIGS. 4 and 5 also provides an area Cdefined by a perimeter of edges 75, 81, 82, and 83 of separatorconstruction 71. Area C is larger than conductor surface area D definedby the shape of tab portion 78 curving edge 84. Thus, tab portion 78 iscentrally positioned within the perimeter of the biomedical electrode.

The structure of electrode 40 and electrode 70 simplifies manufacturingand avoids creation of slits, seams, or cuts to expose thecentrally-positioned tab portion 52 or 78. For example, a strip or otherplurality of electrodes can be arranged on a release liner during makingthe electrodes for facile distribution and application to a subject'sskin

FIG. 6 illustrates a strip 100 of electrodes, which can be eitherelectrodes 40 or electrodes 70. In FIG. 6, the strip 100 of electrodes40 are assembled onto a strip of release liners 102 which areinterconnected at edges having perforated lines 104. The electrode strip100 may be dispensed sequentially or packaged in a folded manner tominimize storage space. At the time of use, as seen in FIG. 6, aperforated line 106 in one liner 102 may be torn to peel electrode 40from liner 102 to expose the field 43 of adhesive(s). It is desirable toplace the perforated line 106 at a location along a line beneath field43 to facilitate removal of electrode 40 from liner 102.

The strip 100 of electrodes 40 or 70 illustrated in FIG. 6 can beassembled with a minimum number of steps, which economizes manufacturingprocesses. FIG. 7 illustrates a method of preparing electrode 40 or 70useful to prepare strip 100.

FIG. 7 shows the construction of an electrode strip subassembly 110which has a laminate construction comprising a strip of conductiveadhesive 112, a strip of separator construction 114, a strip ofdouble-stick adhesive 116, and strip 118 of a series of unseparatedconductor members. Each strip is sequentially aligned as shown in FIG. 7according to processes and with equipment known to those skilled in theart for assembly of laminate constructions including adhesive layers.U.S. Pat. No. 4,795,516 (Strand) and U.S. Pat. No. 4,798,642(Craighead), which are incorporated by reference herein, discloseprocesses and equipment useful for dispensing strips of material fromrolls and overlaying such strips in a registered, continuous manner inorder to prepare a strip subassembly 110. The width of the electrodestrip subassembly 110 is about 2-8 cm and preferably about 4 cm.

At lines 119, the strip subassembly 110 is cut, preferably with astandardized die, to provide a number of individual electrodes 40,having appropriate dimensions, presently preferred to be 1.8 cm wide and4 cm long. Each electrode 40 comprises, in order of assembly from bottomto top and identified with reference to FIG. 2, a field 43 ofadhesive(s), separator construction 41, double-stick adhesive strip 44,and conductor member 42, having a pad portion 53 contacting fieldportion 43a of conductive adhesive, and a tab portion 52 adhered todouble-stick adhesive 44.

As seen again in FIG. 6, each electrode 40 can be applied to a strip 100of release liners 102 by contacting each field 43 of adhesive(s) witheach liner 102. Each electrode 40 is preferably positioned on each liner102 above perforated line 106.

With means known to those skilled in the art to achieve an appropriateregistration, one can place a series of electrodes 40 or electrodes 70on a strip 100 of release liners 102 separated by perforated lines 104,such as that seen in FIG. 6, to minimize complications of biomedicalelectrode construction. U.S. Pat. Nos. 4,795,516 and 4,798,642 discloseprocesses and equipment useful for assuring such registration ofelectrodes between perforated lines 104 and over perforated lines 106.

This method of construction shown in FIG. 6 reduces expense ofmanufacture and permits sequential mass production of biomedicalelectrodes 40 or 70 into a strip of electrode subassembly 110 such asthat seen in FIG. 6 die cut for placement on liners 102 of strip 100.

FIG. 8 illustrates a strip 120 of electrodes, which can be eitherelectrode 40 or electrode 70. In FIG. 8, the strip 120 of electrode 70are assembled onto a release liner 121 during manufacture. The pluralityof electrodes 70 comprising strip 120 can be packaged in a flatcondition to minimize storage space. The number of electrodes 70comprising strip 120 can be adjusted to match the number of electrodes70 to be used in a particular diagnostic or other medical procedure.

Each electrode 70 has a separator construction 71 and a conductor member72 over a field 73 of adhesive(s), except for lift tab portion 74 whichextends beyond field 73.

Each of the electrodes 70 are contiguous to another electrode 70 alonglines 122 and 123. Line 122 separates contiguous electrodes 70 at theirpad portions 77. Lines 123 separate contiguous electrodes 70 betweenadjacent tab portions 78.

FIG. 9 shows the construction of an electrode array subassembly 130 onrelease liner 121. Subassembly 130 has a laminate constructioncomprising a strip 131 of a series of unseparated, mirrored conductormembers, two strips 132 and 133 of double-stick adhesive, two strips 134and 135 of separator construction, and a field 136 of adhesive(s). Eachstrip 131, 132, 133, 134, 135, and 136 is sequentially aligned as shownin FIG. 9 according to processes and with equipment known to thoseskilled in the art for the assembly of laminate constructions includingadhesive layers. U.S. Pat. No. 4,795,516 (Strand) and U.S. Pat. No.4,798,642 (Craighead) disclose processes and equipment useful forpreparing a strip subassembly 130 on release liner 121. The width of theelectrode strip subassembly 130 is about 4-16 cm and preferably about 8cm.

This strip subassembly 130 is sequentially constructed preferably byoverlaying strips 132 and 133, preferably concurrently, on the surfaceof strip 131 which is electrically conductive in a position where padportion 77 becomes tab portion 78, as seen in FIG. 4. Next, strip 134 isapplied to adhesive strip 132 such that separator construction strip 134covers adhesive strip 132 at an area adjacent to edge 82 as seen in FIG.4. Likewise, and preferably concurrently with the overlay of strip 134on strip 132, separator construction strip 135 is laid over adhesivestrip 133 in a symmetrical manner on subassembly 130. Next, depending onwhether conductive adhesive is intended to comprise field 73 or fieldportion 73a, biocompatible adhesive (either conductive adhesive or skinadhesive) is laid over separator construction strips 134 and 135 andconductive adhesive is laid over the area between separator constructionstrips 134 and 135 to contact conductor member strip 131. Preferably, asingle field 136 of conductive adhesive is laid over strip subassembly130 thus far constructed, preferably extending from separatorconstruction strip 134 to separator construction strip 135, except thatfield 136 does not overlay construction strips 134 and 135 in thoseareas distal from conductor member strip 131, in order to createopposing lift tab portions on subassembly 130. Next, the release liner121 is laid over field 136 of adhesive.

Strip subassembly 130 is then separated into individual electrodes 70 asseen in FIG. 8 by cutting along line 122 to bisect subassembly 130 intotwo rows of electrode strips and then cutting along lines 123 toseparate each electrode 70 on release liner 121, thereby producing aplurality of electrodes 70 seen in FIG. 8.

While it is understood that the methods of construction described withrespect to FIG. 7 and the method of construction described with respectto FIG. 9 both apply sequential alignment of multiple layers to form alaminate, the order in which the multiple layers are overlaid may bereversed or otherwise configured. Thus, the method of construction withrespect to FIG. 7 can begin first with conductor members 118 andconclude with conductive adhesive 112, whereas the method ofconstruction with respect to FIG. 9 can begin with release liner 121 andconclude with overlaying of conductor member strip 131.

It is noted that for all embodiments shown and described, the conductormember 42 and 72 was depicted in substantially the same manner, i.e., ashaving a rather large, rectangular, pad portion with an elongate narrowtab portion. It will be understood that a variety of shapes may beutilized; however, the shape described is particularly efficient in thatit provides for a good tab portion readily engagable by a clip, such asclip 7, FIG. 1, and it provides for a pad portion having a relativelylarge surface area

While a variety of materials may be utilized for the conductor member,such as conductor members 16, 42, and 72, preferably the relativelyflat, thin and flexible construction results from a material, such as aplastic material, having a conductive material capable of recoveringelectrical performance after cardiac de-fibrillation procedures such asa silver/silver chloride conductive coating on at least one sidethereof, or an electrically conductive carbon-containing web on at leastone side thereof. If only one side of the conductor member has aconductive layer thereon, it will generally be that side whichcorresponds to the side of the pad portion projecting toward conductiveadhesive, and the portion of the tab portion facing the separatorconstruction.

It is foreseen that a typical conductor member 42 and 72 will comprise astrip of material having a thickness of about 0.05-0.2 millimeters, suchas polyester film having a coating of silver/silver chloride of about2.5-12 micrometers, and preferably about 5 micrometers thick thereon.Presently preferred is a polyester film commercially available as"Mellinex" 505-300, 329, or 339 film from ICI Americas of Hopewell, Va.coated with a silver/silver chloride ink commercially available as"R-300" ink from Ercon, Inc. of Waltham, Mass. For conductor member 42or 72 made of a nonwoven web, a web of polyester/cellulose fiberscommercially available as "Manniweb" web from Lydall, Inc. of Troy, N.Y.having a carbon ink commercially available as "SS24636" ink from AchesonColloids Company of Port Huron, Mich. can be used. To enhance mechanicalcontact between clip 7 and conductor member 42 or 72, anadhesively-backed polyethylene tape can be applied to the conductormember tab portion on the side opposite the side having the conductivecoating A surgical tape commercially available from 3M Company as"Blenderm" tape can be employed for this purpose.

It will be understood that such arrangements are not only flat, thin andflexible, but they will not be likely to render substantial shadows inX-rays. Thus, a patient wearing preferred biomedical electrodesaccording to the present invention can be subjected to X-ray testswithout the need for removal (and accompanying discomfort andinconvenience) and reattachment of the biomedical electrode disclosedherein.

While a variety of shapes and sizes of conductor members may be used,preferred applications involve conductor members with pad portions about1-3 cm by 1-2 cm and tab portions or tongues about 1-3 cm long by0.5-1.5 cm wide.

It will also be understood that a variety of materials may be utilizedas a biocompatible skin adhesive as field portion 43b or 73b. Typically,acrylate ester adhesives will be preferred. Acrylate ester copolymeradhesives are particularly preferred. Such adhesives are generallydescribed in U.S. Pat. Nos. 2,973,826; Re 24,906; Re 33,353; 3,389,827;4,112,213; 4,310,509; 4,323,557; 4,732,808; 4,917,928; 4,917,929 andEuropean Patent Publication 0 051 935, all incorporated herein byreference.

In particular, an adhesive copolymer having from about 95 to about 97weight percent iso-octyl acrylate and from about 5 to about 3 weightpercent acrylamide and having an inherent viscosity of 1.1-1.25 dl/g ispresently preferred.

Adhesive useful as means for adhering 44 or 79 can be any of theacrylate ester adhesives described for the biocompatible skin adhesive.A presently preferred adhesive is the same adhesive as presentlypreferred for the biocompatible skin adhesive except having an inherentviscosity of about 1.3-1.45 dl/g.

For the conductive adhesive, conductive adhesives such as thosedescribed in U.S. Pat. No. 4,848,353 (incorporated herein by reference)will be preferred. In particular, an adhesive having the followingingredients is foreseen as a useful material:

    ______________________________________                                                         Dry Weight Percent                                           ______________________________________                                        Copolymer:                                                                    Acrylic Acid       9.50                                                       N-vinyl pyrrolidone                                                                              9.50                                                       Glycerin           51.58                                                      Guar Gum           0.12                                                       Water              25.50                                                      Sodium hydroxide   2.64                                                       Benzildimethylketal                                                                              0.07                                                       Potassium chloride 1.00                                                       TEGBM (triethylene glycol                                                                        0.09                                                       bis (methacrylate))                                                                              100.00                                                     ______________________________________                                    

It is also preferred to cure the adhesive precursor on a thin supportweb, e.g., 0.1 mm Cerex™ material (available from Monsanto Co., St.Louis, Mo.), to facilitate mechanical handling in manufacturingprocesses.

Separator construction 41 or 71 can be made of a non-conductive naturalor synthetic material, conveniently transparent or translucent materialenabling one to see the condition of conductive adhesive 43 and itscontact with skin of a patient wearing electrode 40 or 70. Presentlypreferred separator construction 41 or 71 is polyethylene terephthalateand between about 0.05 and 0.08 mm thick. A commercially availablepolyethylene terephthalate film is "Mellinex" polyester film from ICIAmericas, Hopewell, Va. having a thickness of 0.05 mm. Alternatively, anadhesively backed polyethylene tape can be used for separatorconstruction 41 or 71. A surgical tape commercially available from 3MCompany as "Blenderm" tape can be employed. The tape can be folded nearpad portion 51 or 77 to create means for adhering 44 or 79. But theadhesive must be covered with spacer to detackify lift tab portion 74.

Again, it will be understood that the previously recited examples areexemplary only of the invention, and the invention is not to be limitedby the specific materials, dimensions, forms or arrangements describedand/or shown in the drawings.

What is claimed is:
 1. A method of making biomedical electrode,comprising:(a) providing a strip of conductive members, each memberhaving two tab portions at opposing edges of the strip and two padportions integral and continuous on the strip; (b) overlaying a meansfor adhering on the strip of conductor members on each tab portion in aposition substantially adjacent to each pad portion; (c) overlaying aseparator construction on each means for adhering and over each tabportion on each conductor member; (d) overlaying a field of conductiveadhesive over each pad portion of each conductive member and optionallyover each separator construction to form an electrode array; (e)overlaying a release liner on the electrode array; (f) cutting theelectrode array on the release liner along a line between adjacent tabportions; and (g) cutting the electrode array along a line betweencontinuous pad portions, whereby a plurality of individual biomedicalelectrodes, each having a centrally-positioned tab portion, are providedon the release liner.
 2. The method according to claim 1, wherein anedge of said separator construction extends beyond an edge of saidconductive adhesive.
 3. The method according to claim 1, furthercomprising between steps (d) and (e) the step of overlaying a field ofbiocompatible skin adhesive over each separator construction.